The present invention relates to a transistorized ignition apparatus, more particularly to an ignition apparatus for driving a plurality of ignition coils at one time.
A transistorized ignition apparatus for driving plural ignition coils in an internal combustion engine, conventionally, has plural power transistors for driving respective ignition coils. Therefore, inherently there is a problem with heat generated by the power transistors and transferred throughout the apparatus. High temperature, as is well-known in the art, causes problems with transistorized apparatus in general and power transistor is particular.
In order to protect a power transistor and an ignition coil and to make constant a voltage induced across a secondary coil of the ignition coil, a transistorized ignition apparatus has been proposed wherein a conduction starting point of the power transistor is controlled and a primary current of the ignition coil is restricted in U.S. Pat. No. 4,030,468. In being adapted for driving plural ignition coils, however, such apparatus necessarily includes plural feedback elements for controlling the conduction starting points of respective power transistors, thereby resulting in a complex construction and an increase in cost.